The present invention related to a fuel injector valve.
A fuel injector valve is described in U.S. Pat. No. 5,299,776. The fuel injector valve has a valve closing member that is connected to a valve needle and interacts with a valve seat surface provided on a valve seat body to form a sealed seat. A magnetic coil, which interacts with a magnetic armature that moves on the valve needle between a first stop limiting the armature movement in the lifting direction of the valve needle and a second stop limiting the armature movement against the lifting direction, is provided for the electromagnetic operation of the fuel injector valve. Within certain limits, the axial armature clearance defined between the two stops isolates the inert mass of the valve needle and the valve closing member from the inert mass of the armature on the other. This counteracts a rebounding of the valve closing member from the valve seat surface within certain limits when the fuel injector valve closes. Bounce pulses of the valve needle and valve closing member cause the fuel injector valve to open briefly in an uncontrolled manner, making it impossible to reproduce the metered amount of fuel and resulting in uncontrolled injection. However, since the axial position of the armature in relation to the valve needle is completely undefined due to the free movement of the armature in relation to the valve needle, bounce pulses can be avoided only to a limited extent. In particular, it is not possible to prevent the armature from striking the stop which faces the valve closing member while the fuel injector valve closes, abruptly transmitting its pulse to the valve needle and thus also to the valve closing member.
To dampen the force of the armature striking the stop facing the valve closing member, a method is described in U.S. Pat. No. 4,766,405, in which a damping member made of an elastomeric material, such as rubber, is placed between the armature and the stop. Elastomeric materials have the disadvantage that their damping performance is highly dependent on temperature, and the damping effect decreases as the temperature rises. In addition, elastomeric materials have a limited long-term stability, particularly when they come into contact with the fuel to be injected. Furthermore, mounting a damping plate made of an elastomeric material is complicated. In addition, it is not possible to selectively adjust the damping characteristics.
The provision of a damping spring in the form of a cup spring between the valve seat body and a valve seat carrier, on which the valve seat body is mounted, thereby causing the valve closing member to come to rest gently against the valve seat surface provided on the valve seat body, is described in U.S. Pat. No. 5,236,173. However, this damping method has the disadvantage that the valve seat body swings back in the direction of injection after the valve closing member strikes the valve seat body, while the valve closing member either remains stationary or even moves away from the valve seat body against the direction of injection as a result of pulse reversal. Valve bounce pulses can therefore occur with even greater intensity in this fuel injector valve design.
The fuel injector valve according to the present invention has the advantage that it can help avoid possible bounce pulses of the valve needle even more effectively. The result is high long-term stability, since the spring element has a longer service life than does an elastomeric material and, in particular, cannot be destroyed when exposed to fuel. It is also possible to selectively adjust the damping characteristics insofar as certain materials, shapes, and pre-tensions can be used for the spring element.
The spring element is used firstly as a lower second stop for the armature; secondly as a damping element that continuously brakes armature movement and thus prevents or greatly limits valve needle bouncing against the valve seat surface; and thirdly as a sliding spring that presses the armature, in its idle position, until it comes to rest on the first stop. With this single spring element component, a very high functional integration can advantageously be achieved.
The spring element according to the present invention can be advantageously produced easily and economically, as well as mounted and adjusted on the valve needle in the fuel injector valve.
The features described in the subclaims provide advantageous embodiments and refinements of the fuel injector valve specified in the main claim.
It is advantageous to design the spring element with a shank and multiple spring arms extended outward from the shank. It is possible to use a spring steel sheet that is formed into a desired mushroom shape by deep-drawing and stamping.